Influence of the N-substituents on the nucleophilicity and Lewis basicity of N-heterocyclic carbenes

Alison Levens, Feng An, Martin Breugst, Herbert Mayr, David Lupton

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61 Citations (Scopus)


The ability to modulate the nucleophilicity and Lewis basicity of N-heterocyclic carbenes is pivotal to their application as organocatalysts. Herein we examine the impact of the N-substituent on the nucleophilicity and Lewis basicity. Four N-substituents popular in NHC organocatalysis, namely, the N-2,6-(CH3O)2C6H3, N-Mes, N-4-CH3OC6H4, and N-tert-butyl groups, have been examined and found to strongly affect the nucleophilicity. Thus, the N-2,6-(CH3O)2C6H3 group provides the most nucleophilic imidazolylidene NHC reported and the N-tert-butyl group one of the least. This difference in nucleophilicity is reflected in the catalyst efficiency, as observed with a recently reported trienyl ester rearrangement.

Original languageEnglish
Pages (from-to)3566-3569
Number of pages4
JournalOrganic Letters
Issue number15
Publication statusPublished - 5 Aug 2016

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